Disclosed herein is a nucleic acid probe for detecting a target nucleic acid. At least one terminal of the probe-binding region in the target nucleic acid is a guanine base, and one or more cytosine bases are present within 1 to 7 bases from the guanine base. The nucleic acid probe comprises an oligonucleotide having a cytosine base facing the guanine base on a terminal and a fluorescent dye conjugated to the cytosine base. The fluorescent dye is quenched by the interaction with a guanine base. The oligonucleotide is completely complementary to the nucleic acid in the probe-binding region except the one or more cytosine bases present within 1 to 7 bases from the terminal guanine base. The base in the oligonucleotide facing the cytosine base closest to the terminal guanine base among the one or more cytosine bases is a base having no fluorescence-quenching effect.